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Dec 9, 2015
12/15
Dec 9, 2015
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Daniel C. Hong; Paul V. Quinn; Stefan Luding
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CanulChay et al. [1] have conducted the segregation experiment of binary granular mixtures in a bed and subjected the bed to vibration. They report that the reverse BrazilNut phenomenon (RBNP) was never observed in their experiments and thus conclude that such does not exist. However, we have clearly demonstrated in [2] by Molecular Dynamics simulations that the reverse BrazilNut problem not only exists, but can be determined from the solidliquid phase boundary by a scaling theory for the...
( 1 reviews )
Source: http://arxiv.org/abs/condmat/0202385v1
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Dec 9, 2015
12/15
Dec 9, 2015
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Paolo Gondolo; Katherine Freese; Douglas Spolyar; Anthony Aguirre; Peter Bodenheimer; Jeremy A. Sellwood; Naoki Yoshida
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The first phase of stellar evolution in the history of the universe may be Dark Stars, powered by dark matter heating rather than by fusion. Weakly interacting massive particles, which are their own antiparticles, can annihilate and provide an important heat source for the first stars in the universe. This and the following contribution present the story of Dark Stars. In this first part, we describe the conditions under which dark stars form in the early universe: 1) high dark matter...
( 1 reviews )
Source: http://arxiv.org/abs/0901.4578v1
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Dec 9, 2015
12/15
Dec 9, 2015
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Simon Gruener; Patrick Huber
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Measurements on helium and argon gas flow through an array of parallel, linear channels of 12 nm diameter and 200 micrometer length in a single crystalline silicon membrane reveal a Knudsen diffusion type transport from 10^2 to 10^7 in Knudsen number Kn. The classic scaling prediction for the transport diffusion coefficient on temperature and mass of diffusing species,D_He ~ sqrt(T), is confirmed over a T range from 40 K to 300 K for He and for the ratio of D_He/D_Ar ~ sqrt(m_Ar/m_He)....
( 1 reviews )
Source: http://arxiv.org/abs/0802.1852v1
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Jul 14, 2015
07/15
Jul 14, 2015
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William H. Butler; Claudia K. A. Mewes; Chunsheng Liu; Tianyi Xu
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We present a rational approach to the design of halfmetallic heterostructures which allows the design of an infinite number of halfmetallic heterostructures. The wide range of materials that can be made halfmetallic using our approach makes it possible to engineer materials with tunable characteristic properties, for example low intrinsic magnetic damping, small magnetic moment or perpendicular anisotropy. We demonstrate the proposed design scheme for a series of transition metal...
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Source: http://arxiv.org/abs/1103.3855v1
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Apr 8, 2015
04/15
Apr 8, 2015
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S. AraujoBetancor; B. T. Gaensicke; K. S. Long; K. Beuermann; D. de Martino; E. M. Sion; P. Szkody
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We have obtained HST/STIS data for a total of eleven polars as part of a program aimed to compile a homogeneous database of highquality farultraviolet (FUV) spectra for a large number of cataclysmic variables (CVs). Of the eleven polars, eight were found in a state of low accretion activity (V347Pav, VVPup, V834Cen, BLHyi, MRSer, STLMi, RXJ1554.2+2721 and V895Cen) and three in a state of high activity (CDInd, ANUMa and UWPic). The STIS spectra of the lowstate polars unambiguously reveal the...
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Source: http://arxiv.org/abs/astroph/0412180v1
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Apr 8, 2015
04/15
Apr 8, 2015
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Michael L. Sitko; Lawrence S. Bernstein; Robert J. Glinski
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We have reanalyzed the ultraviolet spectrum of HD 44179, the central star(s) of the Red Rectangle nebula, providing improved estimates of the column density, rotational, and vibrational temperatures of the 4th Positive AX system of CO in absorption. The flux shortward of 2200 A is a complex blend of CO features with no discernible stellar photosphere, making the identification of other molecular species difficult, and the direct derivation of the dust extinction curve impossible. We confirm...
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Source: http://arxiv.org/abs/0802.2085v1
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Mar 15, 2015
03/15
Mar 15, 2015
by
Mikhail I. Rabinovich; Mehmet K. Muezzinoglu
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We present a new paradigm in the study of brain mental dynamics on the basis of the stable transient activity neural networks observed in experiments. This new approach is in contrast to traditional system analysis usually adopted in cognitive modeling. Transient dynamics offers a sound formalism of the observed qualities of brain activity, while providing a rigorous set of analysis tools. Transients have two main features: First, they are resistant to noise, and reliable even in the face of...
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Source: http://arxiv.org/abs/0909.1144v1
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Jan 26, 2015
01/15
Jan 26, 2015
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Arkaitz Zubiaga; Damiano Spina; Enrique Amigó; Julio Gonzalo
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This paper explores the realtime summarization of scheduled events such as soccer games from torrential flows of Twitter streams. We propose and evaluate an approach that substantially shrinks the stream of tweets in realtime, and consists of two steps: (i) subevent detection, which determines if something new has occurred, and (ii) tweet selection, which picks a representative tweet to describe each subevent. We compare the summaries generated in three languages for all the soccer games in...
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Source: http://arxiv.org/abs/1204.3731v1
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Mar 28, 2014
03/14
Mar 28, 2014
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J. L. F. Barbon
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This is a rendering of a review talk on the state of String Theory, given at the EPS2003 Conference, intended for a wide audience of experimental and theoretical physicists. It emphasizes general ideas rather than technical aspects.
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Source: http://arxiv.org/abs/hepth/0404188v1
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Mar 2, 2014
03/14
Mar 2, 2014
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Roman Sverdlov
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The first goal of this paper is to show that discreteness, locality, and relativistic covariance can peacefully coexist if the ordinary spacetime (OST) is replaced with phase spacetime (PST) as a geometric background of a Poisson process, where PST is a spacetime generalization of a notion of phase space (this is a 7dimensional version of the 8dimensional structure proposed by Caianiello). Furthermore, Caianiello's idea of finite acceleration is implemented. After this is done, the paper then...
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Source: http://arxiv.org/abs/0910.2498v3
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Nov 7, 2013
11/13
Nov 7, 2013
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Andrei A. Galiautdinov; David R. Finkelstein
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The Dirac equation is not semisimple. We therefore regard it as a contraction of a simpler decontracted theory. The decontracted theory is necessarily purely algebraic and nonlocal. In one simple model the algebra is a Clifford algebra with 6N generators. The quantum imaginary $\hbar i$ is the contraction of a dynamical variable whose backreaction provides the Dirac mass. The simplified Dirac equation is exactly Lorentz invariant but its symmetry group is SO(3,3), a decontraction of the...
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Source: http://arxiv.org/abs/hepth/0106273v2
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C. Balázs; E. L. Berger; P. M. Nadolsky; C. P. Yuan
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A fully differential calculation in perturbative quantum chromodynamics is presented for the production of massive photon pairs at hadron colliders. All nexttoleading order perturbative contributions from quarkantiquark, gluon(anti)quark, and gluongluon subprocesses are included, as well as allorders resummation of initialstate gluon radiation valid at nexttonexttoleading logarithmic accuracy. The region of phase space is specified in which the calculation is most reliable. Good...
Source: http://arxiv.org/abs/0704.0001v2
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Ileana Streinu; Louis Theran
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We describe a new algorithm, the $(k,\ell)$pebble game with colors, and use it obtain a characterization of the family of $(k,\ell)$sparse graphs and algorithmic solutions to a family of problems concerning tree decompositions of graphs. Special instances of sparse graphs appear in rigidity theory and have received increased attention in recent years. In particular, our colored pebbles generalize and strengthen the previous results of Lee and Streinu and give a new proof of the...
Source: http://arxiv.org/abs/0704.0002v2
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We show that a determinant of Stirling cycle numbers counts unlabeled acyclic singlesource automata. The proof involves a bijection from these automata to certain marked lattice paths and a signreversing involution to evaluate the determinant.
Source: http://arxiv.org/abs/0704.0004v1
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Wael AbuShammala; Alberto Torchinsky
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In this paper we show how to compute the $\Lambda_{\alpha}$ norm, $\alpha\ge 0$, using the dyadic grid. This result is a consequence of the description of the Hardy spaces $H^p(R^N)$ in terms of dyadic and special atoms.
Source: http://arxiv.org/abs/0704.0005v1
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Y. H. Pong; C. K. Law
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We study the twoparticle wave function of paired atoms in a Fermi gas with tunable interaction strengths controlled by Feshbach resonance. The Cooper pair wave function is examined for its bosonic characters, which is quantified by the correction of Bose enhancement factor associated with the creation and annihilation composite particle operators. An example is given for a threedimensional uniform gas. Two definitions of Cooper pair wave function are examined. One of which is chosen to...
Source: http://arxiv.org/abs/0704.0006v1
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Alejandro Corichi; Tatjana Vukasinac; Jose A. Zapata
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A rather nonstandard quantum representation of the canonical commutation relations of quantum mechanics systems, known as the polymer representation has gained some attention in recent years, due to its possible relation with Planck scale physics. In particular, this approach has been followed in a symmetric sector of loop quantum gravity known as loop quantum cosmology. Here we explore different aspects of the relation between the ordinary Schroedinger theory and the polymer description. The...
Source: http://arxiv.org/abs/0704.0007v2
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A general formulation was developed to represent material models for applications in dynamic loading. Numerical methods were devised to calculate response to shock and ramp compression, and ramp decompression, generalizing previous solutions for scalar equations of state. The numerical methods were found to be flexible and robust, and matched analytic results to a high accuracy. The basic ramp and shock solution methods were coupled to solve for composite deformation paths, such as...
Source: http://arxiv.org/abs/0704.0008v3
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Paul Harvey; Bruno Merin; Tracy L. Huard; Luisa M. Rebull; Nicholas Chapman; Neal J. Evans II; Philip C. Myers
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We discuss the results from the combined IRAC and MIPS c2d Spitzer Legacy observations of the Serpens starforming region. In particular we present a set of criteria for isolating bona fide young stellar objects, YSO's, from the extensive background contamination by extragalactic objects. We then discuss the properties of the resulting high confidence set of YSO's. We find 235 such objects in the 0.85 deg^2 field that was covered with both IRAC and MIPS. An additional set of 51 lower...
Source: http://arxiv.org/abs/0704.0009v1
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Sergei Ovchinnikov
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Partial cubes are isometric subgraphs of hypercubes. Structures on a graph defined by means of semicubes, and Djokovi\'{c}'s and Winkler's relations play an important role in the theory of partial cubes. These structures are employed in the paper to characterize bipartite graphs and partial cubes of arbitrary dimension. New characterizations are established and new proofs of some known results are given. The operations of Cartesian product and pasting, and expansion and contraction processes...
Source: http://arxiv.org/abs/0704.0010v1
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Clifton Cunningham; Lassina Dembele
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In this paper we present an algorithm for computing Hecke eigensystems of HilbertSiegel cusp forms over real quadratic fields of narrow class number one. We give some illustrative examples using the quadratic field $\Q(\sqrt{5})$. In those examples, we identify HilbertSiegel eigenforms that are possible lifts from Hilbert eigenforms.
Source: http://arxiv.org/abs/0704.0011v3
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Recently, Bruinier and Ono classified cusp forms $f(z) := \sum_{n=0}^{\infty} a_f(n)q ^n \in S_{\lambda+1/2}(\Gamma_0(N),\chi)\cap \mathbb{Z}[[q]]$ that does not satisfy a certain distribution property for modulo odd primes $p$. In this paper, using RankinCohen Bracket, we extend this result to modular forms of half integral weight for primes $p \geq 5$. As applications of our main theorem we derive distribution properties, for modulo primes $p\geq5$, of traces of singular moduli and Hurwitz...
Source: http://arxiv.org/abs/0704.0012v1
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Dohoon Choi; YoungJu Choie
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Serre obtained the padic limit of the integral Fourier coefficient of modular forms on $SL_2(\mathbb{Z})$ for $p=2,3,5,7$. In this paper, we extend the result of Serre to weakly holomorphic modular forms of half integral weight on $\Gamma_{0}(4N)$ for $N=1,2,4$. A proof is based on linear relations among Fourier coefficients of modular forms of half integral weight. As applications we obtain congruences of Borcherds exponents, congruences of quotient of Eisentein series and congruences of...
Source: http://arxiv.org/abs/0704.0013v2
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In this article we discuss a relation between the string topology and differential forms based on the theory of Chen's iterated integrals and the cyclic bar complex.
Source: http://arxiv.org/abs/0704.0014v1
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The pure spinor formulation of the tendimensional superstring leads to manifestly supersymmetric loop amplitudes, expressed as integrals in pure spinor superspace. This paper explores different methods to evaluate these integrals and then uses them to calculate the kinematic factors of the oneloop and twoloop massless fourpoint amplitudes involving two and four Ramond states.
Source: http://arxiv.org/abs/0704.0015v2
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ChaoHsi Chang; Tong Li; XueQian Li; YuMing Wang
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In this work, we evaluate the lifetimes of the doubly charmed baryons $\Xi_{cc}^{+}$, $\Xi_{cc}^{++}$ and $\Omega_{cc}^{+}$. We carefully calculate the nonspectator contributions at the quark level where the Cabibbosuppressed diagrams are also included. The hadronic matrix elements are evaluated in the simple nonrelativistic harmonic oscillator model. Our numerical results are generally consistent with that obtained by other authors who used the diquark model. However, all the theoretical...
Source: http://arxiv.org/abs/0704.0016v1
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Nceba Mhlahlo; David H. Buckley; Vikram S. Dhillon; Steven B. Potter; Brian Warner; Patric A. Woudt
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Results from spectroscopic observations of the Intermediate Polar (IP) EX Hya in quiescence during 1991 and 2001 are presented. Spinmodulated radial velocities consistent with an outer disc origin were detected for the first time in an IP. The spin pulsation was modulated with velocities near ~500600 km/s. These velocities are consistent with those of material circulating at the outer edge of the accretion disc, suggesting corotation of the accretion curtain with material near the Roche lobe...
Source: http://arxiv.org/abs/0704.0017v1
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Andreas Gustavsson
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We give a prescription for how to compute the Callias index, using as regulator an exponential function. We find agreement with old results in all odd dimensions. We show that the problem of computing the dimension of the moduli space of selfdual strings can be formulated as an index problem in evendimensional (loop)space. We think that the regulator used in this Letter can be applied to this index problem.
Source: http://arxiv.org/abs/0704.0018v2
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In this note we give a new method for getting a series of approximations for the extinction probability of the onedimensional contact process by using the Gr\"obner basis.
Source: http://arxiv.org/abs/0704.0019v2
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The BABAR Collaboration; B. Aubert
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The shape of the hadronic form factor f+(q2) in the decay D0 > K e+ nue has been measured in a model independent analysis and compared with theoretical calculations. We use 75 fb(1) of data recorded by the BABAR detector at the PEPII electronpositron collider. The corresponding decay branching fraction, relative to the decay D0 > K pi+, has also been measured to be RD = BR(D0 > K e+ nue)/BR(D0 > K pi+) = 0.927 +/ 0.007 +/ 0.012. From these results, and using the...
Source: http://arxiv.org/abs/0704.0020v1
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Vanessa Casagrande; Yuichi Togashi; Alexander S. Mikhailov
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Spatiotemporal pattern formation in a productactivated enzymic reaction at high enzyme concentrations is investigated. Stochastic simulations show that catalytic turnover cycles of individual enzymes can become coherent and that complex wave patterns of molecular synchronization can develop. The analysis based on the meanfield approximation indicates that the observed patterns result from the presence of Hopf and wave bifurcations in the considered system.
Source: http://arxiv.org/abs/0704.0021v2
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Simon J. A. Malham; Anke Wiese
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We present Lie group integrators for nonlinear stochastic differential equations with noncommutative vector fields whose solution evolves on a smooth finite dimensional manifold. Given a Lie group action that generates transport along the manifold, we pull back the stochastic flow on the manifold to the Lie group via the action, and subsequently pull back the flow to the corresponding Lie algebra via the exponential map. We construct an approximation to the stochastic flow in the Lie algebra...
Source: http://arxiv.org/abs/0704.0022v2
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M. A. Loukitcheva; S. K. Solanki; S. White
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The very nature of the solar chromosphere, its structuring and dynamics, remains far from being properly understood, in spite of intensive research. Here we point out the potential of chromospheric observations at millimeter wavelengths to resolve this longstanding problem. Computations carried out with a sophisticated dynamic model of the solar chromosphere due to Carlsson and Stein demonstrate that millimeter emission is extremely sensitive to dynamic processes in the chromosphere and the...
Source: http://arxiv.org/abs/0704.0023v1
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A. A. Serga; M. Kostylev; B. Hillebrands
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The formation of quasi2D spinwave waveforms in longitudinally magnetized stripes of ferrimagnetic film was observed by using time and spaceresolved Brillouin light scattering technique. In the linear regime it was found that the confinement decreases the amplitude of dynamic magnetization near the lateral stripe edges. Thus, the socalled effective dipolar pinning of dynamic magnetization takes place at the edges. In the nonlinear regime a new stable spin wave packet propagating along a...
Source: http://arxiv.org/abs/0704.0024v1
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A. S. Mishchenko; N. Nagaosa
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We present recent advances in understanding of the ground and excited states of the electronphonon coupled systems obtained by novel methods of Diagrammatic Monte Carlo and Stochastic Optimization, which enable the approximationfree calculation of Matsubara Green function in imaginary times and perform unbiased analytic continuation to real frequencies. We present exact numeric results on the ground state properties, Lehmann spectral function and optical conductivity of different strongly...
Source: http://arxiv.org/abs/0704.0025v1
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Robert P. C. de Marrais
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Zerodivisors (ZDs) derived by CayleyDickson Process (CDP) from Ndimensional hypercomplex numbers (N a power of 2, at least 4) can represent singularities and, as N approaches infinite, fractals  and thereby,scalefree networks. Any integer greater than 8 and not a power of 2 generates a metafractal or "Sky" when it is interpreted as the "strut constant" (S) of an ensemble of octahedral vertex figures called "BoxKites" (the fundamental building blocks of...
Source: http://arxiv.org/abs/0704.0026v3
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M. O. Goerbig; J. N. Fuchs; K. Kechedzhi; Vladimir I. Fal'ko
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We describe a peculiar fine structure acquired by the inplane optical phonon at the Gammapoint in graphene when it is brought into resonance with one of the interLandaulevel transitions in this material. The effect is most pronounced when this lattice mode (associated with the Gband in graphene Raman spectrum) is in resonance with interLandaulevel transitions 0 > (+,1) and (,1) > 0, at a magnetic field B_0 ~ 30 T. It can be used to measure the strength of the electronphonon...
Source: http://arxiv.org/abs/0704.0027v4
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Péter E. Frenkel
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We prove pfaffian and hafnian versions of Lieb's inequalities on determinants and permanents of positive semidefinite matrices. We use the hafnian inequality to improve the lower bound of R\'ev\'esz and Sarantopoulos on the norm of a product of linear functionals on a real Euclidean space (this subject is sometimes called the `real linear polarization constant' problem).
Source: http://arxiv.org/abs/0704.0028v2
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Zhan Shu; XiaoLin Chen; WeiZhen Deng
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In $\XQM$, a quark can emit Goldstone bosons. The flavor symmetry breaking in the Goldstone boson emission process is used to intepret the nucleon flavorspin structure. In this paper, we study the inner structure of constituent quarks implied in $\XQM$ caused by the Goldstone boson emission process in nucleon. From a simplified model Hamiltonian derived from $\XQM$, the intrinsic wave functions of constituent quarks are determined. Then the obtained transition probabilities of the emission of...
Source: http://arxiv.org/abs/0704.0029v2
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J. P. Hague; N. d'Ambrumenil
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We investigate the effect of tuning the phonon energy on the correlation effects in models of electronphonon interactions using DMFT. In the regime where itinerant electrons, instantaneous electronphonon driven correlations and static distortions compete on similar energy scales, we find several interesting results including (1) A crossover from band to Mott behavior in the spectral function, leading to hybrid band/Mott features in the spectral function for phonon frequencies slightly larger...
Source: http://arxiv.org/abs/0704.0030v1
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A. EstebanPretel; R. Tomàs; J. W. F. Valle
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We analyze the possibility of probing nonstandard neutrino interactions (NSI, for short) through the detection of neutrinos produced in a future galactic supernova (SN).We consider the effect of NSI on the neutrino propagation through the SN envelope within a threeneutrino framework, paying special attention to the inclusion of NSIinduced resonant conversions, which may take place in the most deleptonised inner layers. We study the possibility of detecting NSI effects in a Megaton water...
Source: http://arxiv.org/abs/0704.0032v1
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Liming Wang; Eduardo D. Sontag
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The multisite phosphorylationdephosphorylation cycle is a motif repeatedly used in cell signaling. This motif itself can generate a variety of dynamic behaviors like bistability and ultrasensitivity without direct positive feedbacks. In this paper, we study the number of positive steady states of a general multisite phosphorylationdephosphorylation cycle, and how the number of positive steady states varies by changing the biological parameters. We show analytically that (1) for some parameter...
Source: http://arxiv.org/abs/0704.0036v2
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Jose A. Oller; Luis Roca
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The quadratic pion scalar radius, \la r^2\ra^\pi_s, plays an important role for present precise determinations of \pi\pi scattering. Recently, Yndur\'ain, using an Omn\`es representation of the null isospin(I) nonstrange pion scalar form factor, obtains \la r^2\ra^\pi_s=0.75\pm 0.07 fm^2. This value is larger than the one calculated by solving the corresponding MuskhelishviliOmn\`es equations, \la r^2\ra^\pi_s=0.61\pm 0.04 fm^2. A large discrepancy between both values, given the precision,...
Source: http://arxiv.org/abs/0704.0039v2
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As in the cases of freeness and monotonic independence, the notion of conditional freeness is meaningful when complexvalued states are replaced by positive conditional expectations. In this framework, the paper presents several positivity results, a version of the central limit theorem and an analogue of the conditionally free Rtransform constructed by means of multilinear function series.
Source: http://arxiv.org/abs/0704.0040v3
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Debashish Goswami
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We formulate a quantum generalization of the notion of the group of Riemannian isometries for a compact Riemannian manifold, by introducing a natural notion of smooth and isometric action by a compact quantum group on a classical or noncommutative manifold described by spectral triples, and then proving the existence of a universal object (called the quantum isometry group) in the category of compact quantum groups acting smoothly and isometrically on a given (possibly noncommutative) manifold...
Source: http://arxiv.org/abs/0704.0041v4
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R. A. Brownlee; A. N. Gorban; J. Levesley
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We construct a system of nonequilibrium entropy limiters for the lattice Boltzmann methods (LBM). These limiters erase spurious oscillations without blurring of shocks, and do not affect smooth solutions. In general, they do the same work for LBM as flux limiters do for finite differences, finite volumes and finite elements methods, but for LBM the main idea behind the construction of nonequilibrium entropy limiter schemes is to transform a field of a scalar quantity  nonequilibrium entropy....
Source: http://arxiv.org/abs/0704.0043v1
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A. A. Schekochihin; S. C. Cowley; W. Dorland; G. W. Hammett; G. G. Howes; E. Quataert; T. Tatsuno
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We present a theoretical framework for plasma turbulence in astrophysical plasmas (solar wind, interstellar medium, galaxy clusters, accretion disks). The key assumptions are that the turbulence is anisotropic with respect to the mean magnetic field and frequencies are low compared to the ion cyclotron frequency. The energy injected at the outer scale scale has to be converted into heat, which ultimately cannot be done without collisions. A KINETIC CASCADE develops that brings the energy to...
Source: http://arxiv.org/abs/0704.0044v4
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G. A. El; R. H. J. Grimshaw; A. M. Kamchatnov
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This paper considers the propagation of shallowwater solitary and nonlinear periodic waves over a gradual slope with bottom friction in the framework of a variablecoefficient Kortewegde Vries equation. We use the Whitham averaging method, using a recent development of this theory for perturbed integrable equations. This general approach enables us not only to improve known results on the adiabatic evolution of isolated solitary waves and periodic wave trains in the presence of variable...
Source: http://arxiv.org/abs/0704.0045v1
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I. Csiszar; F. Hiai; D. Petz
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In a quantum mechanical model, Diosi, Feldmann and Kosloff arrived at a conjecture stating that the limit of the entropy of certain mixtures is the relative entropy as system size goes to infinity. The conjecture is proven in this paper for density matrices. The first proof is analytic and uses the quantum law of large numbers. The second one clarifies the relation to channel capacity per unit cost for classicalquantum channels. Both proofs lead to generalization of the conjecture.
Source: http://arxiv.org/abs/0704.0046v1
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T. Kosel; I. Grabec
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The intelligent acoustic emission locator is described in Part I, while Part II discusses blind source separation, time delay estimation and location of two simultaneously active continuous acoustic emission sources. The location of acoustic emission on complicated aircraft frame structures is a difficult problem of nondestructive testing. This article describes an intelligent acoustic emission source locator. The intelligent locator comprises a sensor antenna and a general regression neural...
Source: http://arxiv.org/abs/0704.0047v1